Modified acrylic adhesive systems have achieved acceptance as substitutes for mechanical fastening methods. Fundamental to the performance of such adhesive systems is their ability to provide both the rigidity required for high tensile strength and the toughness and flexibility required for high peel and impact resistance. Initially, anaerobic adhesives were introduced as locking and sealing compounds. Although these adhesives were capable of improving the strength and reliability of threaded fasteners and sealing leaks they did not possess the flexibility and toughness of a true structural adhesive.
One approach to overcoming the inflexibility of the adhesive is to combine dimethacrylates and urethanes. The modified acrylics are normally solutions of mono-methacrylate monomers and polymeric rubbers. There are also systems available which are made using higher molecular weight mono-methacrylates, which impart greater flexibility to these adhesives. In general, however, both types of systems are two-part systems similar to epoxys. In these systems, one part consists of the polymer, monomer or initiator, while the other part contains the activator. All of these systems require mixing and measuring prior to their being applied to the structure to be bonded.
Therefore, what is required in this art is a two-component, modified acrylic adhesive which does not require any premixing or measuring prior to its application to the substrate to be bonded. In addition, such an adhesive should possess the properties of a true structural adhesive, such as good flexibility and toughness.